. Results of a biological survey of Mount Shasta, California. Natural history; Natural history. TIMBERLINE. 27 tbein oil over an almost level tiiict with sucli resistless Ibroe tliat tbe few now left staiuling are deeply scarred at a height of 10 to 15 feet above the ground, showing where they were struck by other trees in passing over the deep snow. Hundreds of huge trunks 75 to 100 feet long and .> or 4 feet in diameter are strewn ill desolate conriision over the broad area tliat marks the place where this terrific avalanche slowed lip and linally stopped. The accompanying illustration sh
. Results of a biological survey of Mount Shasta, California. Natural history; Natural history. TIMBERLINE. 27 tbein oil over an almost level tiiict with sucli resistless Ibroe tliat tbe few now left staiuling are deeply scarred at a height of 10 to 15 feet above the ground, showing where they were struck by other trees in passing over the deep snow. Hundreds of huge trunks 75 to 100 feet long and .> or 4 feet in diameter are strewn ill desolate conriision over the broad area tliat marks the place where this terrific avalanche slowed lip and linally stopped. The accompanying illustration shows a part of this area, and also the gate cut by the avalanche when it struck the upper edge of the Fig. 13.—Track of avalanche invading forest of Shasta firs on Cold Creek, east side of Shasta. TIMBERLINE. Timberline is the upper or boreal limit of tree growth, as determined by temperature. It varies somewhat according to the particular species of tree, for even Hudsonian species differ in the degree of cold they are able to endure. Thus in the northern Cascades where the alpine hemlock and alpine flr are the dominant timberline trees, the fir pushes up to higher altitudes than the hemlock. So on Shasta, where the alpine fir is replaced by the white-bark pine, the latter is the true tim- berline tree and always attains higher elevations than the hemlock. Theoretically, nothing is easier than tracing timberline on a moun- tain whose upper slopes are bare or dotted with alpine flowers and whose middle slopes support a continuous forest. Yet on Shasta, and on most high mountains, it is exceedingly difficult to fix the boundary of timberline or indicate its exact position on a map. Of course, it is. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Merriam, C. Hart (Clinton Hart), 1855-1942. Washingto
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